The combination of pmprintf and pmflush produces output in either an xconfirm(1) window, on the standard error stream, or to a file in a manner similar to fprintf(3). The fmt argument is used to control the conversion, formatting, and printing of the variable length args list. The output technique is controlled via an environment variable.

pmprintf appends the formatted message string to an internal buffer shared by the two routines, without actually producing any output.

pmflush causes the internal buffer to be either displayed in a window, printed on standard error, or flushed to a file and the internal buffer to be cleared.

The environment variable PCP_STDERR controls the output technique used by pmflush:

If PCP_STDERR is unset, the text is written onto the stderr stream of the caller.

If PCP_STDERR is set to the literal reserved word DISPLAY then the text will be displayed as a GUI dialog using xconfirm(1).

If PCP_STDERR is set to any other value then pmflush interprets the value as a file name and appends the text to that file. The file is created if it doesn't already exist, and in this case if the file creation fails, then stderr is used instead).